1. Field of the Invention
The present invention relates to a spread illuminating apparatus particularly a spread illuminating apparatus used as an illuminating means for a liquid crystal display.
2. Description of the Related Art
A liquid crystal display operating in low power consumption features low profile and light weight and there is a growing demand therefor mainly in a computer field. Since a liquid crystal which is a component of the liquid crystal display does not emit light by itself unlike a light emitting element such as a cathode-ray tube, an illuminating means for observing an image is separately required. According to the recent specific demand for lower profile configuration, there has been a growing tendency to employ a spread illuminating apparatus of thin-plate side light type (light conductive-plate type) as an illuminating means for the liquid crystal display.
An example of such a side light type spread illuminating apparatus is shown in FIG. 5.
In FIG. 5, a spread illuminating apparatus 1 is generally composed such that a bar-like light conductive member 5 is disposed along one end surface 3 of a transparent substrate 2 made of a light-transmissible material, a spot-like light source 6 mounted on a flexible printed circuit board (FPC) 6A is disposed on one end of the light conductive member 5 and that a frame 9 is held to the transparent substrate 2 so as to cover the light conductive member 5 and the spot-like light source 6.
The frame 9 is generally composed of a base plate 9a facing the end surface 3 of the transparent substrate 2 with the light conductive member 5 and the spot-like light source 6 interposed therebetween, two opposing plates (the opposing plates on upper and lower sides in FIG. 5 are referred to as an xe2x80x9cupper opposing plate 9bxe2x80x9d and a xe2x80x9clower opposing plate 9cxe2x80x9d, respectively) continuous with and substantially orthogonal to the base plate 9a and opposing each other in such a manner as to clamp a portion 8 (hereinafter referred to as a xe2x80x9ctransparent substrate proximal portionsxe2x80x9d) positioned toward the end surface 3 of the transparent substrate 2, and two extension plates 9d bent at both ends of the upper opposing plate 9b so as to face each other.
The frame 9 is disposed so as to house the spot-like light source 6 and the light conductive member 5 with the upper opposing plate 9b and the lower opposing plate 9c touching the transparent substrate proximal portion 8, respectively.
In the spread illuminating apparatus, since the spot-like light source and the light conductive member are fitted in the frame to be assembled, a certain clearance D is required between the frame 9 and the spot-like light source 6 or the light conductive member 5 as shown in FIG. 6, and a clearance E is apt to be present between the spot-like light source 6 and the light conductive member 5.
However, when the clearances D and E are present as described above, light utilization efficiency (the total efficiency) is deteriorated. Accordingly, the presence of any clearance is not desirable for effectively maintaining the light utilization efficiency.
Further, when large spot-like light source and light conductive member are employed, the extension plates 9d are pressed with the spot-like light source 6 and the light conductive member 5 and move outward as shown in FIG. 7 in the above conventional art. Consequently, the frame 9 is not applicable for the large spot-like light source and light conductive member.
The present invention has been made in the light of the above problems, and an object of the present invention is to provide a spread illuminating apparatus capable of ensuring excellent light utilization efficiency while maintaining workability in assembling.
According to a first aspect of the present invention, in a spread illuminating apparatus in which a bar-like light conductive member is disposed along at least one end surface of a transparent substrate made of a light-transmissible material, a spot-like light source is disposed on at least one end of the light conductive member, and in which a frame is held to the transparent substrate so as to cover the light conductive member and the spot-like light source, the frame generally comprises a base plate facing an end surface of the transparent substrate with the light conductive member and the spot-like light source interposed therebetween, two opposing plates continuous with the base plate and opposing each other in such a manner as to clamp the transparent substrate at a portion toward the end surface thereof, and two extension plates bent at both ends of at least one of the two opposing plates so as to face each other, with at least one extension plate having a spring force working toward the other extension plate.
According to a second aspect of the present invention, in the spread illuminating apparatus of the first aspect of the present invention, the two extension plates are provided on one opposing plate disposed on an observation surface side of the transparent substrate.